/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.search.highlight;

import java.io.IOException;
import java.util.Collections;
import java.util.Iterator;
import org.apache.lucene.index.BinaryDocValues;
import org.apache.lucene.index.ByteVectorValues;
import org.apache.lucene.index.DocValuesSkipIndexType;
import org.apache.lucene.index.DocValuesSkipper;
import org.apache.lucene.index.DocValuesType;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.Fields;
import org.apache.lucene.index.FloatVectorValues;
import org.apache.lucene.index.IndexOptions;
import org.apache.lucene.index.LeafMetaData;
import org.apache.lucene.index.LeafReader;
import org.apache.lucene.index.NumericDocValues;
import org.apache.lucene.index.PointValues;
import org.apache.lucene.index.SortedDocValues;
import org.apache.lucene.index.SortedNumericDocValues;
import org.apache.lucene.index.SortedSetDocValues;
import org.apache.lucene.index.StoredFieldVisitor;
import org.apache.lucene.index.StoredFields;
import org.apache.lucene.index.TermVectors;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.VectorEncoding;
import org.apache.lucene.index.VectorSimilarityFunction;
import org.apache.lucene.search.AcceptDocs;
import org.apache.lucene.search.KnnCollector;
import org.apache.lucene.util.Bits;
import org.apache.lucene.util.Version;

/**
 * Wraps a Terms with a {@link org.apache.lucene.index.LeafReader}, typically from term vectors.
 *
 * @lucene.experimental
 */
public class TermVectorLeafReader extends LeafReader {

  private final Fields fields;
  private final FieldInfos fieldInfos;

  public TermVectorLeafReader(String field, Terms terms) {
    fields =
        new Fields() {
          @Override
          public Iterator<String> iterator() {
            return Collections.singletonList(field).iterator();
          }

          @Override
          public Terms terms(String fld) throws IOException {
            if (!field.equals(fld)) {
              return null;
            }
            return terms;
          }

          @Override
          public int size() {
            return 1;
          }
        };

    IndexOptions indexOptions;
    if (!terms.hasFreqs()) {
      indexOptions = IndexOptions.DOCS;
    } else if (!terms.hasPositions()) {
      indexOptions = IndexOptions.DOCS_AND_FREQS;
    } else if (!terms.hasOffsets()) {
      indexOptions = IndexOptions.DOCS_AND_FREQS_AND_POSITIONS;
    } else {
      indexOptions = IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS;
    }
    FieldInfo fieldInfo =
        new FieldInfo(
            field,
            0,
            true,
            true,
            terms.hasPayloads(),
            indexOptions,
            DocValuesType.NONE,
            DocValuesSkipIndexType.NONE,
            -1,
            Collections.emptyMap(),
            0,
            0,
            0,
            0,
            VectorEncoding.FLOAT32,
            VectorSimilarityFunction.EUCLIDEAN,
            false,
            false);
    fieldInfos = new FieldInfos(new FieldInfo[] {fieldInfo});
  }

  @Override
  protected void doClose() throws IOException {}

  @Override
  public Terms terms(String field) throws IOException {
    return fields.terms(field);
  }

  @Override
  public NumericDocValues getNumericDocValues(String field) throws IOException {
    return null;
  }

  @Override
  public BinaryDocValues getBinaryDocValues(String field) throws IOException {
    return null;
  }

  @Override
  public SortedDocValues getSortedDocValues(String field) throws IOException {
    return null;
  }

  @Override
  public SortedNumericDocValues getSortedNumericDocValues(String field) throws IOException {
    return null;
  }

  @Override
  public SortedSetDocValues getSortedSetDocValues(String field) throws IOException {
    return null;
  }

  @Override
  public DocValuesSkipper getDocValuesSkipper(String field) throws IOException {
    return null;
  }

  @Override
  public NumericDocValues getNormValues(String field) throws IOException {
    return null; // Is this needed?  See MemoryIndex for a way to do it.
  }

  @Override
  public FieldInfos getFieldInfos() {
    return fieldInfos;
  }

  @Override
  public Bits getLiveDocs() {
    return null;
  }

  @Override
  public PointValues getPointValues(String fieldName) {
    return null;
  }

  @Override
  public FloatVectorValues getFloatVectorValues(String fieldName) {
    return null;
  }

  @Override
  public ByteVectorValues getByteVectorValues(String fieldName) {
    return null;
  }

  @Override
  public void searchNearestVectors(
      String field, float[] target, KnnCollector knnCollector, AcceptDocs acceptDocs) {}

  @Override
  public void searchNearestVectors(
      String field, byte[] target, KnnCollector knnCollector, AcceptDocs acceptDocs) {}

  @Override
  public void checkIntegrity() throws IOException {}

  @Override
  public TermVectors termVectors() throws IOException {
    return new TermVectors() {
      @Override
      public Fields get(int docID) {
        if (docID != 0) {
          return null;
        } else {
          return fields;
        }
      }
    };
  }

  @Override
  public int numDocs() {
    return 1;
  }

  @Override
  public int maxDoc() {
    return 1;
  }

  @Override
  public StoredFields storedFields() throws IOException {
    return new StoredFields() {
      @Override
      public void document(int docID, StoredFieldVisitor visitor) throws IOException {}
    };
  }

  @Override
  public LeafMetaData getMetaData() {
    return new LeafMetaData(Version.LATEST.major, null, null, false);
  }

  @Override
  public CacheHelper getCoreCacheHelper() {
    return null;
  }

  @Override
  public CacheHelper getReaderCacheHelper() {
    return null;
  }
}
